A web page that is downloaded to a client browser includes markup language, potentially some multi-media files, and potentially some script code. The markup language is most commonly HyperText Markup Language (HTML) and is interpretable by the browser to define structure of the web page, along with some or potentially all of the content. The multi-media files may include video or images rendered automatically within the layout of the web page, or that may be rendered in response to execution of one or more controls. The script code allows the page to have more dynamic functionality and may be executed automatically and/or in response to a user interacting with controls on the page. Javascript is an example of a script coding language.
The web page typically includes one or more elements. As the web page is rendered, each element is positioned within the web page. Some user interface platforms allow multiple layout processes to be performed in sequence for the element. For instance, an element may first have a default position that it would have absent any direction. The web page itself may override this default position by containing an expression of the element's position. For instance, in the context of a HyperText Markup Language (HTML) web page, this is called the “in-flow” position. Style sheets may also apply other layout positions that would further change this position. When multiple layout processes are applied, they are typically applied in sequence. Once the final layout is determined, the element may be rendered in its proper position.